The present invention relates to a carbody connection system for cranes, such as mobile lifting crane that uses crawlers mounted on a carbody. The invention provides a connection system so that carbody members can be easily separated and reconnected at each job site.
Mobile lift cranes typically include a carbody having moveable ground engaging members; a rotating bed rotatably connected to the carbody such that the rotating bed can swing with respect to the ground engaging members; a boom pivotally mounted on a front portion of the rotating bed, with a load hoist line extending there from, and counterweight to help balance the crane when the crane lifts a load. There are different types of ground engaging members, most notably tires for truck mounted cranes, and crawlers. The crawlers typically have a frame, at least one drive tumbler supported on the frame; and a track made of a plurality of connected track shoes wrapped around the frame and engaging the drive tumbler so that a plurality of the shoes are in contact with the drive tumbler. Many cranes have two crawlers, one on each side of the carbody. However, there are some cranes that have four crawlers, two on each side of the carbody.
Since a crane will often be used in various locations, it needs to be designed so that it can be transported from one job site to the next. Moving a crane can be a formidable task when the machine is large and heavy. For example, highway limits on vehicle-axle loads must be observed and overhead obstacles can dictate long, inconvenient routings to the job site. One solution to improving the mobility of large construction machines, such as cranes, is to disassemble them into smaller, more easily handled components. The separate components can then be transported to the new job site where they are reassembled. For example, the typical practice has been to disconnect, remove, and transport the crawlers separately from the crane carbody. For a very large crane, it may also be necessary to separate the carbody into individual members. The ease with which the crane can be dismantled and set up has an impact on the total cost of using the crane. Thus, to the extent that fewer man-hours are needed to set up the crane, there is a direct advantage to the crane owner
In conventional cranes, each of the crawlers is typically bolted to the carbody of the crane. Because the connections between the crawlers and the crane carbody must sustain tremendous loads, the size and number of bolts used in these connections can be substantial. Accordingly, removing each of the crawlers from the carbody of the crane usually requires the loosening and removal of numerous large bolts from each of the crawler to carbody connections. Once the crane components are delivered to the new job site, then the crawlers must be carefully aligned with the carbody, and each of the bolts must then be re-inserted and tightened for each of the crawler-to-carbody connections. As a consequence, the disconnection and re-connection of the crawlers to the crane can be a difficult and time-consuming process.
For the carbody itself, there have been crane designs where the carbody was assembled from parts at a job site. One particular design had a central section with two end sections that attached to the central section. Thus the carbody size was limited to a maximum size of what could be transported on three separate transport trailers. One of the other problems with known prior designs is that the ring gear and roller path, which are typically carried on the carbody when the crane is operating, had to be added to the carbody after it was assembled. This is a time consuming process, since normally the ring gear and roller path sections are bolted onto the carbody. Including those pieces on the carbody sections presents a difficulty because the pieces, once assembled, have to match up very closely. However, when trying to manipulate large carbody sections and attach them together at a jobsite, it is easier to make the assembly if the sections can be brought together by lowering one piece next to the other piece, and having a connection system that relies on the weight of the piece being lowered to draw the pieces together as the connection is made. However, with this type of connection, it is difficult to get ring gear and roller path sections already bolted to the carbody sections close enough to one another to provide a smooth roller path and uninterrupted ring gear. Another difficulty arises if the components are all distinct and have to be staged for delivery at the job site in just the right order so that the next piece to be added to the assembly arrives next. Thus there remains a need for a carbody that can be easily taken apart into more than three pieces and transported and then reassembled at a new job site, and a carbody that can be taken apart into transportable sections that each include portions of the ring gear.